# Simple question but still can't figure it outsound

#### emma123

i am having trouble with this question" if you clap your hands the echo from a distant wall 0.20s later, how far away is the wall?" how do you do this without the speed given to substitute into the speed= distance/time equation?

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#### xman

usually you may take the speed of sound in air around ~340 m/s at room temperature. remember also that the sound goes to the wall and back, when you hear it, so this will effect your calculation. hope this help, sincerely, x

#### emma123

o thanks for the speed of sound. so all i have to do is plug it in, but then remember to divide by 2 for the distance to get 34 m.?

#### sebas531

emma123 said:
...but then remember to divide by 2 for the distance...
well, if you mean divide the time by 2 in order to get the distance yes. If you are using 340 as the speed of sound yes it will give you 34m, although your teacher or your book might have 34.3m depending on what your book of your teacher is using as the speed of sound which with no disrespect to x-man some books say that the speed of sound at room temperature is 343m/s.

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